Emil said:
"That would be CSRCs or audio level header extensions as per RFC6465."
[BA] As I understand it, the CSRCs are needed to determine who is contributing to the audio at a given time.
Since you're not trying to compose a list of conference participants from RTP (e.g. you get this from signaling), a list of the CSRCs isn't helpful.
This would suggest that you are looking for an event, yes?